A communication system using a relay is actively under research to improve communication efficiency. For example, a system for delivering a signal by using the relay is researched and developed to solve a situation in which a User Equipment (UE) cannot receive a service when located outside a coverage area of a Base Station (BS) or when located in a shadowing zone.
Conventionally, the relay performs a function of simply storing data received from a source node in a network and thereafter delivering the stored data to a destination node. However, in order to effectively use a network resource and to improve transmission efficiency, a network coding scheme has recently been proposed in which a plurality of pieces of data received from a plurality of source nodes are encoded together and are transmitted to a plurality of destination nodes. For example, as illustrated in FIG. 1, instead of directly transmitting data x received from a UE #1 101 and data y received from a UE #2 102, a relay 110 encodes the data x and y by using an eXclusive OR (XOR) operation and thereafter transmits encoded data x⊕y to the UE #1 101 and the UE #2 102. In addition, instead of directly transmitting data w received from a UE #3 103 and data z received from a UE #4 104, the relay 110 encodes the data w and z by using the XOR operation and thereafter transmits encoded data z⊕w to the UE #103 and the UE #4 104.
As such, when using the network coding scheme, each UE may extract desired data on the basis of data retained in each UE from data received from a network. For example, as illustrated in FIG. 1, when the UE #1 101 receives the encoded data x⊕y from the relay, since the data x is pre-known, the data y may be extracted from the encoded data x⊕y on the basis of the data x.
However, since data encoded using the network coding scheme is determined according to a scheduling scheme used in the relay, even if the UE receives encoded data including desired data, there may be a case where the desired data cannot be extracted when all other pieces of data encoded together are not known, and also there may be a case where encoding data not including the desired data is received. In this case, the UE needs to persistently wait until data which is decodable with data retained in the UE and which includes desired data is received.